"Here's my favorite little fact. If anyone is ever described to you as a nutritionist, just be slightly wary, right? What they're saying may be perfectly true, but "nutritionist" isn't a protected term. Anyone can call themselves a nutritionist. "Dietician" is the legally protected term. "Dietician" is like "dentist", and "nutritionist" is like "tooth-i-ologist."
Dara Ó Briain Talks Funny: Live in London (2008)